Transmissions of wind turbines usually have a lubricant pump in order to supply lubrication points with lubricant by lubricant circulation. Such transmissions are exposed to high loads. A breakdown of the lubrication supply can therefore give rise to severe damage in a short time, which ultimately results in failure of the wind turbine.
To avoid this, emergency lubrication systems are used in wind turbines. Such devices serve to ensure the supply of lubricant to the transmission during emergency operation, i.e. in the event that a lubricant pump provided for normal operation has failed.
From the document DE 10 2008 013 728 A1 an emergency lubrication device with two pumps is known. A first, electrically driven pump supplies the transmission with lubricant during normal operation. For emergency operation a second pump is switched on. Its function has to be ensured even if the electric power is cut off. Accordingly, the second pump is not driven electrically. Instead, a clutch is provided which for emergency operation establishes a force flow between the transmission and the second pump.
To actuate the clutch a control element is provided. During normal operation, i.e. when a voltage is applied, the control element is activated. The activated control element opens the clutch. A spring is attached in such manner that when the clutch is open, the spring is stressed.
When during emergency operation there is no longer any voltage and the first pump is therefore inactive, the control element to is no longer active. Consequently, the spring relaxes and the clutch closes. This brings the second pump into the force flow of the transmission. The lubricant supply is ensured until the wind turbine has stopped.
The use of a second pump to create an emergency lubrication system has a number of disadvantages. The second pump increases the manufacturing costs of the transmission. Moreover, additional lines and connections are required in order to integrate the second pump into the lubricant circuit of the transmission. All the additional components incorporated also increase the weight of the transmission and take up additional space.
A further disadvantage relates to actuation of the control element. The lubricant supply can only be maintained when the energy supply fails, but not if the first pump becomes defective. Since the control element is only deactivated when voltage is no longer applied, i.e. when the energy supply to the wind turbine has failed, a defect of the first pump—which can also happen when the energy supply has not failed and a voltage is still being applied—results in a breakdown of the lubricant supply.